1. Field of the Invention
This invention relates generally to the field of methylation status of genes and regulatory elements and more specifically to detection of prostate cancer by conventional and quantitative PCR methods.
2. Background Information
Prostatic adenocarcinoma is the most commonly diagnosed non-cutaneous cancer for men in the United States. The incidence is likely to continue to increase as people survive longer and more middle-aged men undergo routine screening for the disease. Men diagnosed with early stage small volume disease have the best outcome following curative treatment. Therefore the aim of early detection programs is to diagnose cancer at an early curable stage.
The gold standard algorithm for diagnosis currently entails digital rectal exam and measurement of serum prostate-specific antigen (PSA) and if either is suspicious it is followed by trans-rectal prostatic needle biopsy. However, serum PSA can be elevated in benign conditions and needle biopsy may fail to identify even significant amounts of cancer due to sampling error. Therefore, the introduction of additional diagnostic tests is needed to improve the sensitivity of prostate cancer diagnosis.
Although several specific genetic alterations have been described in prostate adenocarcinoma, such as TP53 and PTEN inactivation, the single most common and earlier of these is methylation of the 5′-regulatory region of the GSTP1 gene. The detection of this epigenetic alteration in bodily fluids has been successfully accomplished using DNA-based techniques. However, these earlier studies either included only a relatively small number of patients or focused mainly on cases of advanced disease.
Recently, a specific real-time quantitative methyl specific PCR (RTQ-MSP) method, allowing the performance of non-isotopic, rapid, and highly accurate quantitative amplification analysis via the continuous optical monitoring of a fluorogenic PCR assay was developed. The application of this method to evaluate the methylation status of the p16 gene in bone marrow aspirates from patients with multiple myeloma, revealed complete concordance with conventional MSP (C-MSP) analysis. In this same study, it was shown that RTQ-MSP was sensitive enough to detect down to 10 genome equivalents of methylated p16 sequence.
However, there is a need in the art to develop sensitive and accurate early stage diagnostic assays for detecting prostate adenocarcinoma.